[Johnythree]

I'm puzzled by this claim. I wouldn't call it a myth, but all the same...

I grew up on a vineyard. Each harvest time the grapes would hang down heavily and almost touch the ground. Our pet dogs would park themselves beneath and greedily consume a whole bunch.

They would also scoff any dried grapes they found on the ground.

The worst effect seemed that they all would get noticeably pudgy during the season.

[florbo]

The concentration of tartaric acid in each individual grape is unpredictable, along with each individual dog's tolerance level to tartaric acid. The only thing that's certain is that anything with tartaric acid is potentially toxic to canines due the development kidney damage after ingestion.